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Tuesday, 28 June 2016

Upgrading the Micro Kossel round 2

So, after the last time I upgraded the Micro, I did some motion testing and found that the new effector was trading increased print height for build radius, in other words it was limiting prints to half of the physical build plate with a slightly taller maximum height. I decided to see if I could do better. Starting with the E3D Lite6 Documentation, I imported the STL of the original effector into my favourite 3D modeling program and designed a new effector that raised the heatsink above the effector and supported nozzle cooling fans.

Micro Kossel with upgraded raised effector

Designing this new effector was far from simple, my first steps were basically creating a digital mock-up of the Lite6 and it's fan ducting along with removing the center holes from the mesh for the effector platform, took about 2 days of work and research to finish that part. Next was deciding where to put the nozzle fans and not interfere with the motion mechanics. My basic idea was to place the fans at the top of the hot-end, tilted about 30 degrees down from horizontal, and with the nozzle just below the bottom of the effector.

Effector version 1 with one fan installed for testing

As you can see, not the best design, mainly because I forgot to allow for the wiring harness! That gap near the front is my attempt to correct the issue with a wood chisel, not particularly effective and not something I'd do again. For my second iteration, I decided to move the effector so it's just above the wiring, basically made it shorter, the design work was fairly quick this time, so I printed version 2 the next day.

Effector V2

Version 1 (left) and Version 2 (right)

Effector V2 with fans and Kapton tape

V2 with hot-end half installed

Hot-End clamp with mounting screws

For the non-printed parts I'm using a pair of 3010 box fans with 2 of the corners cut off, 6 M3x20mm screws, and 2 M3x10mm screws.

V2 with hot-end fully clamped

This solved the wiring issue, so I proceeded to install the rest of the components, only to find that the fans protruded too far from the effector and jammed against the rod arms, not much of an improvement over the 'tuna can' effector. So back to the drawing board for version 3.

Version 2 (Left) and Version 3 (Right)

For Version 3, I moved the fans upwards so they are fully above the hot-end and rotated them 180 degrees so the lowest edge is pointing inwards towards the Bowden tube, not outwards. As you'll probably notice, the v3 prototype's fan mounts are a bit rough around the edges, that's because my Mini Kossel was being glitchy about printing V3, just some kinked filament, so I cut the fan mounts off the V1 and epoxyed them to the incomplete V3 print.

V3 with Hot-end installed

Version 3 fully assembled

All that remained was to attach the rod-arms and test the range of motion, the V3 design allows the effector to practically touch the drive belts without issue, and adds a full 5 cm to the maximum build height, bringing the maximum build volume up to a 13 cm diameter by 11 cm high cylinder.You can find the stls for the raised effector here: BodyClampNon-printed parts:2 3010 case fans with 2 corners removed (see photos above)2 M3x10mm screws for the hot-end clamp6 M3x20mm screws for mounting the fans and hot-end clamp